[HN Gopher] Quantum researchers cause controlled 'wobble' in the...
___________________________________________________________________
Quantum researchers cause controlled 'wobble' in the nucleus of a
single atom
Author : gmays
Score : 50 points
Date : 2024-09-19 13:58 UTC (9 hours ago)
(HTM) web link (www.tudelft.nl)
(TXT) w3m dump (www.tudelft.nl)
| notum wrote:
| CTRL+F "entanglement". Disappointed.
|
| No interstellar comms for us.
| roywiggins wrote:
| Entanglement isn't particularly useful for communication, you
| can't send bits without sending photons (or similar)
| physically. Quantum mechanics doesn't permit ansibles as far as
| anyone knows.
| josefritzishere wrote:
| I had to google ansible.
| https://en.wikipedia.org/wiki/Ansible
| aatd86 wrote:
| Is it the issue or is it rather than any measurement of
| entangled quantum state change is modifying the measurement
| to the extent that there is a chicken and egg problem?
|
| Basically reading quantum data is also a write operation?
| eigenket wrote:
| The issue the person above is alluding to is known as the
| no communication theorem.
|
| It has a wiki page
|
| https://en.m.wikipedia.org/wiki/No-communication_theorem
|
| But the upshot is basically that entanglement doesn't let
| you do anything unless you send some classical data as
| well.
| aatd86 wrote:
| Thanks. The reason still seem to be related to the
| uncertainty principle although I am not sure.
|
| The same way they explain no-cloning but it seems to be
| analogous to identity within a system with interaction
| from neighboring data. Ultimately there is no pure
| independent state. Data always exists within context.
| Hence causality and spatial preservation (no instant
| physical teleportation as far as is currently
| understood). (in very layman's terms)
| eigenket wrote:
| While the second and third parts if your comment are complete
| true, the first part
|
| > Entanglement isn't particularly useful for communication
|
| I would say is false. Entanglement lets you do some fun and
| theoretically useful stuff for communication tasks. At the
| most basic level sharing entanglement lets you upgrade a
| classical communication channels you have into a quantum one
| (sending 2 bits and burning an entangled pair lets you send a
| qubit). You can do increasing fancy stuff if you so wish, if
| you are sufficiently paranoid you might be interested in
| device independent cryptography, which is only possible
| because of entanglement.
| roywiggins wrote:
| Yes, they are fun, but not notably useful, at least not
| yet. And only useful for pretty specialized tasks like key
| exchange.
| quantadev wrote:
| Isn't it true that in key exchange entanglement isn't
| used in any way shape or form for sending data, but only
| in making a determination that there was no eavesdropping
| on the transmission, because any eavesdropper would
| collapse the wave function.
|
| So like you said, entanglement can't be used to send
| information, but it can be used to detect if the
| transmission was secure (I think)
| eigenket wrote:
| There are many protocols for quantum key
| distribution/exchange so it's hard to answer fully
| without knowing which one you're talking about. That said
| their are protocols, like the one invented by Artur Ekert
| in 1991, which use entanglement in an essential way to
| transmit the key. Even in the absence of an evesdropper
| the protocol will not work without entanglement. It
| escapes the no-communication theorem by _also_ requiring
| some classical communication.
| bloopernova wrote:
| I am unable to grasp why FTL communication would break
| causality, it's like my brain just refuses to accept it.
| Seriously, I've had it explained several times over the
| years.
| shepardrtc wrote:
| When you communicate, you're sending energy - whether it's
| sound waves or radio waves or whatever. Energy can't travel
| faster than c through spacetime. Now if you manipulate
| spacetime, such as a wormhole or whatever, then the end
| result can effectively appear as if it's FTL but its still
| going at c, its just traveling through less/compressed
| space.
| eigenket wrote:
| Its probably mostly because you have an intuitive idea that
| there is some concept of "now" which is independent of the
| observer.
|
| In special relativity this global "now" isn't a thing. It
| doesn't exist. There is no global now. Different observers
| who are in different places and/or moving at different
| speeds will describe different events as simultaneous.
|
| In particular say we have an observer who sees an event A
| happening at time 0, and a second event (call it B) at time
| t and the distance between them is greater than c t. Then
| you can find observers who see A happening first, B
| happening first or the two happening at the same time.
| However all observers will agree that the distance between
| the events was greater than c times the time between them.
|
| This seems like it would cause problems with causality, but
| it doesn't because we need the distance to be greater than
| c times the time, which means no lightspeed signal could
| get from A to B. If you allow ftl communication then this
| "escape" doesn't work anymore, and causality can be
| explicitly broken.
| rogerclark wrote:
| You can't grasp this because there is no FTL communication.
| Quantum entanglement does not enable FTL communication, and
| wormholes etc. are entirely theoretical.
| roywiggins wrote:
| It doesn't even enable STL communication, other than eg
| superdense coding and similar. But that's not what people
| mean when they think entanglement can be used for
| communication.
| Ono-Sendai wrote:
| https://forwardscattering.org/post/36
| roywiggins wrote:
| If you did manage FTL communication, it seems like it
| might let you detect the notional absolute rest frame, so
| you'd be breaking special relativity anyway.
| bloopernova wrote:
| That post is very straightforward, thank you!
| bitwize wrote:
| There was a young lady named Bright, Whose speed
| was much faster than light. She went out one day
| In a relative way And returned on the previous
| night.
|
| Time flows differently depending on velocity with respect
| to your frame of reference. Two observers moving at
| different speeds with respect to each other see different
| time flows. At normal speeds this is negligible but at
| close to light speed... hoo boy. You get things like
| observers seeing events occur separately that occured
| simultaneously for their counterparts and so forth. So _if_
| you were able to send information faster than light
| somehow, you would be sending it from one frame of
| reference with one notion of time into another frame of
| reference with a different notion of time -- one which
| observes receipt of the message before it can observe the
| sender sending it!
|
| It's all a big ball of wibbly-wobbly, timey-wimey stuff.
| quantadev wrote:
| One intuitive explanation is that anything moving at the
| speed of light is experiencing no time at all (from the
| point of view of an observer) and if something is moving
| faster than light that means it's going _backwards_ in
| time. (only massless virtual particles can)
|
| If a clock stops or runs backwards that totally messes up
| "causality" which is about events interacting relative to a
| time order, and so time must exist for causality to make
| sense.
| unsupp0rted wrote:
| For MRI / medical imaging, if nuclear wobbling can enhance signal
| strength, it might be possible to achieve high-quality images
| using lower-strength magnetic fields, and much faster. Maybe even
| ones that fit in a backpack and unfold.
| pbhjpbhj wrote:
| For comparison, it seems the smallest portable MRI presently
| are ~600kg, like the Hyperfine Swoop
| https://hyperfine.io/swoop/overview (not affiliated).
| gaze wrote:
| I'm not totally sure what makes this result so novel but also
| that's probably due to my ignorance. Hyperfine qubits are pretty
| common using neutral atoms, and you can do imaging on the
| hyperfine states. Is the novelty here that the electron spin is
| on resonance with the nuclear spin and that it's done with STM? I
| guess I don't see how pump-probe is so much more direct than
| using an imaging transition.
| quantadev wrote:
| I think the key thing they were pointing out was the ability to
| store information inside a nucleus that can be read back
| (reminds me of how core memory worked on the old Apollo 11 Era
| computers) which could be a very reliable and dense memory.
| It's reliable because the electron shell is sort of protecting
| the information stored inside the nucleus.
|
| I wonder if they'll have the same issue that core memory also
| had which is that by reading the magnetic state you also
| destroy that state, and so every bit 'read' operation has to be
| followed with a 'now write the bit back again' step.
| acidburnNSA wrote:
| Big dream of mine would be to align nuclei of nuclear fuel atoms
| just so and then induce fission in such a way as to get one
| delayed neutron precursor and one other quick-to-stability
| fission product. This would allow fission power without any long-
| lived waste products or afterglow heat cooling challenges that
| dominate accident risk. Physicist friends have told me it's
| impossible. I've only accepted impractical for now.
| AtlasBarfed wrote:
| You want an msr/LFTR and breed away the bad waste.
| colechristensen wrote:
| You're thinking about the atom very classically, At the scale
| of the nucleus things just don't "exist" in "places". Processes
| are truly random and things literally don't have
| position/momentum/rotation/alignment until you do the thing
| that requires them to decide where they were and what they were
| doing at the time.
|
| Simpler than nuclear physics is just the electron. There is no
| meaningful answer to where it is around an atom at any
| particular time. You can either get a location or a momentum or
| half the information about each if you poke it, but that's just
| its response to being poked, it wasn't "actually" there until
| you poked it.
| im3w1l wrote:
| From what I recall, quantum things have well defined _states_
| , even if those states may not correspond to _position /
| momentum / rotation / alignment_.
|
| By correctly molding the energy landscape it may be possible
| to set the states and state transitions up in a beneficial
| way for what he proposed.
| colechristensen wrote:
| Eh, not really. You can futz with the probability
| distribution, like a fast neutron will cause a different
| distribution of fission products than a slow one... but it
| is still a very random process. You can't control it like
| an expert at a billiards table. Especially the strong force
| mediated interactions between particles in the nucleus.
| Some people just won't believe you though.
| fooker wrote:
| > Processes are truly random
|
| You can get a Nobel prize or two by proving this.
|
| We don't know about random yet, just that there's no hidden
| variable.
| fooker wrote:
| In software terms, this would be as difficult as switching out
| specific bits from a running program to fix bugs.
|
| Certainly not impossible, but impractical as far as we can see.
___________________________________________________________________
(page generated 2024-09-19 23:00 UTC)